Beverage-making machines, in particular espresso machines, are increasingly being designed for the use of portion capsules which are filled with a certain quantity of pulverulent or liquid beverage base materials. The most common portion capsules here comprise either a cup which is deep-drawn from aluminium foil, and is closed in an air-tight and aroma-tight manner by a lid closure element made of aluminium foil, or a cup which is thermoformed from plastics material or a plastics-material cup which is produced by injection moulding, and is closed in an air-tight and aroma-tight manner by a lid closure element made of aluminium foil or plastics-material film.
The beverage-making machines which are suitable for accommodating, and extracting the contents from, such a portion capsule are provided with a brewing or preparation chamber which preferably comprises a fixed, first chamber part, which is provided with opening means for beverage-discharge purposes and is connected in a fluid-channelling manner to a structure for the outflow of the beverage, and also comprises a second chamber part, which can be moved horizontally or vertically in relation to the first chamber part, is connected in a fluid-channelling manner, in order for the portion capsule to be supplied with the extraction liquid, to an extraction-liquid-feeding subassembly and is provided with at least one piercing means for opening the portion capsule, and for the introduction of the extraction liquid into the portion capsule, wherein the brewing or preparation chamber is opened in order for a portion capsule to be accommodated and is closed in order for the portion capsule to have its contents extracted.
For the brewing operation, the piercing means penetrate into the portion capsule—either on the side thereof which is closed by the film or foil or on the base side thereof—and the extraction liquid, which is pumped under pressure into the brewing chamber, can flow into the portion capsule through the openings pierced by the piercing means. In order for the resulting beverage to drain out, the portion capsule, depending on the respective portion-capsule system, is opened on the side located opposite the extraction-liquid-feeding side. In the case of portion capsules which are produced from a plastics material and are closed by a plastics-material closure film or aluminium foil, this takes place by means of a portion-capsule-opening spike arranged on the base of the brewing or preparation chamber.
In the case of portion capsules which are produced from an aluminium foil and are closed by a lid closure element made of aluminium foil, the aluminium closure foil rests on the points of a pyramid plate arranged on the base of the brewing chamber and, by means of the pressure which is built up in the portion capsule by the extraction liquid flowing under pump pressure into the portion capsule, the aluminium closure foil is pushed against the pyramid points such that the foil is pierced by the pyramid points and the portion capsule is thus opened. The aluminium closure foil here is designed for a certain rupture pressure, as a result of which, prior to the pyramid points piercing through the closure foil, in particular for the preparation of an espresso, the coffee granules are subjected to optimum moistening and pressure action, which is essential for optimum crema formation, which is the marker of quality for a good espresso. Once the portion capsule has been opened, the coffee brew flows out of the brewing chamber via drainage channels.
In the case of brewing- or preparation-chamber systems which are designed for the use of portion capsules which consist of an aluminium foil and are closed by a lid closure element made of aluminium foil, there is a risk of use being made of system-incompatible portion capsules which consist, in full or in part, of plastics material, correspond to the configuration of the original portion capsule and are thus accepted by the accommodating device of the brewing or preparation chamber. The fact that the system-related construction of the brewing or preparation chambers for portion capsules consisting of an aluminium foil has to be different from that of brewing or preparation chambers for portion capsules consisting of non-metallic material means that the use of portion capsules which consist, in full or in part, of plastics material may result in considerable disruption to the operation of the beverage-making machine or in inferior preparation results.